CD spectroscopy background
A circular dichroism (CD) spectrometer measures differential absorbance of left- and right-hand circularly polarized light, which provides the basis for the conformational analysis of macromolecules. Since the far-UV CD spectra are distinct for the respective secondary structure elements of proteins (such as a-helix and ß-sheet), the protein secondary structure can be determined. In addition, the CD spectral features in the near-UV region provide insights into the tertiary structure of proteins. CD spectroscopy is also employed in the structural studies of nucleic acids. Common CD applications include:
1. Determination of the protein secondary structure (facilitated by the CDPro software package).
2. Characterization of the protein secondary structure dependence on a variety of solvent conditions (for example, varying pH or ionic strength).
3. Examination of protein/nucleic acid stability (unfolding and refolding) by the addition/removal of a denaturant or increasing/decreasing temperature.
4. Evaluation of changes in protein/nucleic acid structure induced by ligand binding.
AVIV 202 CD spectrometer
The AVIV 202 circular dichroism (CD) spectrometer measures differential absorbance of left- and right-hand circularly polarized light in the 170-875 nm wavelength range. A Peltier temperature control system facilitates data collection at -10oC to 110oC, and a titrator attachment allows for an automated solvent composition modification. In addition, the Aviv 202 CD instrument is equipped with a stopped-flow accessory that allows for rapid mixing of reagents in kinetics experiments.